JP6826310B2 - Electrodes for discharge lamps and their manufacturing methods - Google Patents

Description

The present invention relates to an electrode for a discharge lamp and a method for manufacturing the same, and more particularly to an electrode used for a short arc type discharge lamp and a method for manufacturing the same.

Conventionally, a short arc type discharge lamp filled with mercury has a short distance between the tips of a pair of electrodes arranged facing each other in the arc tube and is close to a point light source. Therefore, an exposure device having high light collection efficiency when combined with an optical system. It is used as a light source for
Further, a short arc type discharge lamp containing xenon is used as a visible light light source in a projector or the like, and in recent years, it is also heavily used as a light source for digital cinema.
The market demands that this type of discharge lamp have higher illuminance, and that the amount of light emitted from the short arc type discharge lamp also increases.
It has been conventionally known that the amount of radiated light of a short arc type discharge lamp is proportional to the electric input to the discharge lamp. That is, the amount of radiated light can be increased by increasing the electric input to the discharge lamp.
However, when the lamp current is increased, the electrode is heated, the evaporation of the electrode material such as tungsten is promoted, and the inner wall of the arc tube may be blackened. In particular, when the lamp current increases, the tip of the anode is heated by the increase in the electron flow, the temperature of the anode rises, and when the discharge to the outside is insufficient, the anode material that accompanies the temperature rise of the anode There are problems such as accelerated evaporation and shortened lamp life.

In order to solve such a problem, it has been proposed to improve the efficiency of heat radiation from the anode and lower the temperature of the anode.
For example, Japanese Patent Application Laid-Open No. 2002-117806 (Patent Document 1) discloses that the anode is composed of a tip portion, a cone portion, and a body portion, and a V-shaped groove portion is formed on a side surface of the body portion. ..
By providing such a groove structure, the heat emissivity from the surface of the anode is improved, the heat generated by lighting the lamp is efficiently radiated, the temperature of the anode is lowered, and tungsten and the like are scattered from the anode. Evaporation can also be suppressed.

By the way, the electrode of the discharge lamp is exposed to radiation from a high-temperature arc near the tip, and becomes a high temperature of 2000 ° C. or higher, so that the electrode is easily deformed during the lighting process. Further, since the heat flowing into the electrode is radiated and conducted, a material having a high density is preferable as the material of the electrode. Therefore, conventionally, a powder of a refractory metal such as tungsten is sintered, and then forging or forging is performed. A sintered body (solid material) that has been subjected to HIP treatment (Hot Isostatic Pressing) and the like to have a high density has been used.
The shape of the solid wood used for the electrodes is rod-shaped, and since tungsten is a difficult-to-cut material, the machining time is long except for cutting with a lathe, which is not realistic.
Therefore, in most cases, the shape of the electrode is restricted to an axisymmetric shape based on a cylinder.
Therefore, there is a problem that it is difficult to reduce the weight of the electrode and it is difficult to save resources of the electrode material such as tungsten.

JP-A-2002-117806

In view of the above-mentioned problems of the prior art, the present invention aims to reduce the weight of the electrode for a discharge lamp made of a tungsten material, at the same time, saves resources of the electrode material, and discharges with an excellent heat dissipation function. It provides an electrode structure for a lamp and a method for manufacturing the same.

In order to solve the above problems, the electrode for a discharge lamp of the present invention has a structure in which a main body made of a tungsten powder melt laminate is laminated on a tip made of a tungsten sintered body, and the tungsten of the main body is made of tungsten. It is characterized in that the relative density is made smaller than the relative density of tungsten at the tip portion.
Further, the relative density of tungsten on the outer peripheral portion of the main body portion is made smaller than the relative density of the central portion.
Further, the sintered body constituting the tip portion is a forged sintered body, and the longitudinal direction of the tungsten crystal grains at the tip portion extends in the electrode axial direction.
Further, it is characterized in that a heat radiation groove extending in the electrode axial direction is formed on the outer peripheral surface of the main body portion.
Further, the method for manufacturing an electrode for a discharge lamp is characterized in that a powder fused deposition model of tungsten is laminated and modeled on a rear end portion of a sintered body of tungsten.

According to the present invention, the tip of the electrode, which becomes hot when exposed to the arc, is made of a high-density sintered body in order to radiate and conduct the heat flowing into the electrode, and the main body, which is the rear part of the electrode, has a low density. Since the powder melt laminate is used, the weight of the entire electrode can be reduced as compared with the conventional one in which the entire electrode is made of a sintered body, and the resource saving of tungsten, which is an electrode material, is promoted.
Further, since the powder melt laminate is composed of a porous tungsten layer, the heat radiation characteristics from the side surface of the electrode can be improved and the temperature of the electrode can be lowered.
Further, since the electrode main body is made of a powder melt laminate, the shape has a degree of freedom, and an electrode having an arbitrary shape can be created.

Sectional drawing of 1st Example (A) and 2nd Example of the electrode for a discharge lamp of this invention. An enlarged cross-sectional view of part A in FIG. An enlarged cross-sectional view of part B in FIG. An example of a laminated modeling apparatus for manufacturing the electrodes of the present invention. The explanatory view of the manufacturing process 1 of the electrode of this invention. The explanatory view of the manufacturing process 2 of the electrode of this invention. The explanatory view of the manufacturing process 3 of the electrode of this invention. The explanatory view of the manufacturing process 4 of the electrode of this invention. The explanatory view of the manufacturing process 5 of the electrode of this invention. The explanatory view of the manufacturing process 6 of the electrode of this invention. The final process diagram of the electrode of this invention. A front view (A) and a side view (B) of a third embodiment of the electrode of the present invention. Explanatory drawing of the laser metal deposition apparatus which manufactures an electrode of this invention.

1 (A) and 1 (B) show the electrode 1 for a discharge lamp of the present invention, and the electrode 1 shown in FIG. 1 (A) has a tip 11 made of a sintered tungsten body (solid body) and the tip portion 11. The main body 12 made of a tungsten powder molten laminate is laminated on the eleven. The core wire 2 is inserted and fixed at the rear end of the main body portion 12.
In this example, the sintered body of the tip portion 11 is forged after sintering tungsten to increase the density (hereinafter, also referred to as a sintered forged body).
The main body 12 made of the powder melt laminate is made of a porous tungsten layer, and the relative density of the tungsten is smaller than the relative density of the tip 11 made of the sintered body. For example, the relative density of the tip portion 11 is 99.5%, and the relative density of the main body portion 12 is 95%.
Here, the relative density of tungsten means the ratio (%) to the theoretical density of 19.3 g / cm ³ .
In the electrode 1 shown in FIG. 1B, the main body 12 is composed of two first main bodies 12a and a second main body 12b having different relative densities, and the relative density of the second main body 12b is the first main body 12a. Smaller than For example, the tip portion 11 is 99.5%, the first main body portion 12a is 95%, and the second main body portion 12b is 90%.

FIG. 2 shows an enlarged cross section of the A portion of FIG. 1, that is, the boundary region between the tip portion 11 and the main body portion 12, and the sintered body constituting the tip portion 11 is forged after sintering. It is a body, and the longitudinal direction of the tungsten particles 11a exists along the electrode axial direction. Such a particle arrangement can be obtained by considering the forging direction of tungsten and the cutting direction of the tip portion 11. That is, since the longitudinal directions of the tungsten particles 11a are aligned in the direction orthogonal to the forging direction, the tip portion 11 may be prepared so that the longitudinal direction is the electrode axial direction. As a result, many grain boundaries are present on the joint surface with the main body portion 12.
Therefore, when the main body portion 12 which is a powder melt laminate is laminated on the tip portion 11, the tungsten particles on the main body portion 12 side are melted and bite into the grain boundaries of many tungsten particles 11a on the tip portion 11 side. , The bonding strength between the tip portion (sintered forged body) 11 and the main body portion (powder molten laminate) 12 becomes strong.

Further, FIG. 3 shows an enlarged cross-sectional view of the portion B of FIG. 1, in which the relative density of tungsten in the outer peripheral portion thereof is made smaller than the relative density in the central portion. As a result, a low-density tungsten pore layer 12c is formed on the side surface of the main body 12, for example, on the surface layer of several tens of μm to several hundreds of μm, and the gap between the tungsten particles is used as a pseudo black body to radiate the electrode surface. The emissivity can be further increased and the temperature of the electrode can be lowered.

In the above embodiment, the sintered body constituting the tip portion 11 has been described as an example of a sintered forged body forged after sintering, but as described above in paragraph 0004, the sintered body is not forged. The density may be increased by the HIP treatment of.

Next, an example of the method for manufacturing the electrode of the present invention will be described below.
FIG. 4 shows a laminated molding device 5 for manufacturing the electrode for a discharge lamp of the present invention, and the laminated molding device 5 supplies a laminated stage 51 for laminating and molding tungsten powder, and a tungsten powder Y. The powder supply stage 52, the squeegee 53 that transfers the tungsten powder from the powder supply stage 52 to the lamination stage 51, the fiber laser 54 that generates the laser light L that solidifies the tungsten powder, and the fiber laser 54 that reflects the laser light L to cover the tungsten powder. It has a galvanometer 55 to scan.

The laminating stage 51 and the powder supply stage 52 are movable up and down, and the squeegee 53 can be moved from the powder supply stage 52 to the laminating stage 51.
The galvano mirror 55 reflects the laser beam L emitted from the fiber laser 54 toward the tungsten powder on the laminated stage 51. By driving the galvano mirror 55, the laser beam L is scanned in a predetermined pattern.
In addition, in order to prevent the tungsten powder from being oxidized when it solidifies, it is preferable to arrange at least the lamination stage 51 in the inert gas.

The method of manufacturing the electrode by the laminated modeling apparatus 5 will be described with reference to FIGS. 5 to 11.
In FIG. 5, a tungsten sintered body X having a predetermined shape and thickness constituting the electrode tip portion 11 is placed on the laminated stage 51, and the tungsten powder Y is placed on the powder supply stage 52. It is loaded.
In this state, the laminating stage 51 is lowered by a predetermined distance, and the powder supply stage 52 is raised by a predetermined distance. As a result, as shown in FIG. 6, the surface of the stacking stage 51 is lowered, and in the powder powder supply stage 52, the tungsten powder Y is fed upward.

Next, as shown in FIG. 7, the squeegee 53 moves from the powder supply stage 52 toward the lamination stage 51, scrapes the tungsten powder Y on the powder supply stage 52, transfers it to the lamination stage 51, and bake it. It is loaded so as to cover the top of the body X. In FIG. 8, in a state after the movement of the squeegee 53 is completed, the sintered body X on the loading stage 51 is covered with the tungsten powder Y and buried.

As shown in FIG. 9, the laser beam L is emitted from the fiber laser 54, reflected by the galvanometer mirror 55, and irradiated to the tungsten powder Y on the loading stage 51. The laser beam L is scanned according to a predetermined shape of the main body 12, and at the condensing point, the tungsten powder Y is melted and solidified to form the tip 11 as shown in FIG. A thin layer of a powder melt laminate made of tungsten is formed on the body X. However, in this case, not all of the tungsten powder Y is melted, and some of the tungsten powder Y is in a sintered state.

By repeating the same procedure thereafter, as shown in FIG. 11, an electrode 1 in which the main body portion 12 made of the powder melt laminate is laminated in a predetermined shape is formed on the tip portion 11 made of the sintered body. ..
Here, when the main body portion 12 is laminated, the tungsten density of the powder molten laminate can be controlled by the amount (thickness) of the coated powder material, the energy of the laser beam, the scanning speed of the laser beam, and the like. ..
As a result, the relative density of the main body portion 12 to be laminated can be made arbitrarily small with respect to the relative density of the tungsten of the tip portion 11.

Further, as shown in FIG. 1B, the main body portion 12 can be configured by two first main body portions 12a and second main body portions 12b having different relative densities.
Further, as shown in FIG. 3, the structure may be such that the relative density of tungsten on the outer peripheral portion of the main body portion 12 is smaller than the relative density of the central portion. By doing so, the emissivity of the surface of the electrode body 12 can be increased and the temperature of the electrode can be further lowered.
As described above, such a relative density gradient can be achieved by controlling the energy of the laser beam, the scanning speed, and the like.

As described above, since the main body 12 is made of a powder melt laminate, any shape can be created, and as shown in FIG. 12, a heat radiation groove 13 extending in the pipe axis direction is provided on the outer peripheral surface of the main body 12. It can also be formed. When the entire electrode is made of a forged sintered body, such a heat radiation groove is generally formed by cutting by laser processing, but in the present invention in which the main body 12 is made of a powder melt laminate, the main body is molded. Occasionally, a heat dissipation groove can be formed at the same time, which greatly improves workability.

By the way, the powder molten laminate constituting the main body portion 12 can be molded by the laser metal deposition method in addition to the molding by the laminated molding apparatus 5.
The molding method is disclosed in, for example, Japanese Patent Application Laid-Open No. 2015-038237, and the main part configuration thereof is shown in FIG.
The laser metal deposition device 6 has a cylindrical multiple nozzle, the laser light L is emitted from the laser light nozzle 61 in the center to the work W, and the tungsten powder Y is supplied from the material ejection nozzle 62 around the laser light L. .. The supplied powder material Y is sintered or melted by laser light to form a desired thin film. A shield gas supply nozzle 63 is formed on the outside of the material ejection nozzle 62, and for example, argon gas G is flowed to prevent oxidation.
According to this laser metal deposition method, the work W is irradiated with the laser beam L, and the tungsten powder Y is injected into the irradiated area, so that the tungsten powder is built up with the laser beam, so that the lamination speed is high. There is.

As described above, the electrode for the discharge lamp of the present invention has a structure in which the main body portion made of a porous powder molten laminate is laminated on the tip portion made of a sintered body, so that the tip portion can cope with high heat due to an arc. Since the main body, which is the rear part where the temperature is relatively low, is a tungsten layer with a reduced relative density, the weight of the entire electrode can be reduced and the resource saving of tungsten, which is an electrode material, is promoted. Will be done.
Further, since the main body is a porous tungsten layer, the heat radiation characteristics from the side surface of the electrode are improved, which contributes to the temperature decrease of the entire electrode.
Further, the shape of the main body has a degree of freedom, and an electrode having an arbitrary shape such as a heat dissipation groove can be created.

1 Electrode 11 Tip (sintered body)
11a Tungsten particles 12 Main body (powder melt laminate)
12a 1st main body 12b 2nd main body 12c Pore layer 13 Heat dissipation groove 2 Core wire 5 Laminated molding device 51 Laminated stage 52 Powder supply stage 53 Squeegee 54 Fiber laser 55 Galvano mirror 6 Laser metal deposition device 61 Laser light nozzle 62 Material Ejection nozzle 63 Shield gas supply nozzle X Sintered body Y Tungsten powder L Laser light G Shield gas (argon gas)

Claims (3)

It is composed of a tip portion made of a sintered body of tungsten and a main body portion made of a powder melt laminate of tungsten laminated on the tip portion.
The sintered body constituting the tip portion is a forged sintered body, and the longitudinal direction of the tungsten crystal grains at the tip portion extends in the electrode axial direction.
An electrode for a discharge lamp, characterized in that the relative density of tungsten in the main body is made smaller than the relative density of tungsten in the tip. The electrode for a discharge lamp according to claim 1 , wherein a heat radiation groove extending in the electrode axial direction is formed on the outer peripheral surface of the main body portion. It consists of a tip made of a sintered tungsten body and a main body made of a powder melt laminate of tungsten laminated on the tip, and the relative density of tungsten in the main body is the relative density of tungsten in the tip. A method for manufacturing electrodes for smaller discharge lamps.
A method for manufacturing an electrode for a discharge lamp, which comprises laminating a tungsten powder fused deposition body on the rear end portion of a tungsten sintered body.

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